The goal of this application, entitled "Gastroenteritis and Extreme Weather Events in Elderly (GEWEL)" is to examine how temporal and spatial patterns of gastrointestinal diseases (GID) respond to extreme weather events at the national and regional levels. We postulate that variability in the GID incidence in the elderly is sensitive to a change in meteorological parameters. We assume that frequency and intensity of extreme weather events, such as heat waves, droughts, heavy rainfalls and floods, can alter the incidence of food borne and waterborne infections. We expect that the effect of extreme events on health will depend on vulnerability of the affected population and the geographical area. In the proposed study we will: 1) examine the effect of extreme temperature and precipitation on severity and composition of food borne and waterborne infections among the elderly in Massachusetts using -50,000 laboratory-confirmed cases and approximately 100,000 hospitalization records of six enteric diseases (1992-2004); 2) assess the impact of extreme weather events on hospitalizations for acute GID in the US elderly across climatic zones using nation-wide dataset of approximately 2,500,000 hospitalization records (1984-2004); and 3) develop, test and implement analytical models for assessing long-term, intermediate, and short-term effects of an extreme event on GID. A multidisciplinary team is fully capable of completing an integrated project that will explore a complex system of health and environmental interactions and develop novel methodology which will have important implications for environmental and health policy. Reliable, objective and accurate estimates of incidence of enteric infection related to environmental stressors, better understanding of mechanisms of human environmental interactions, and the impact of socio-economic and demographic factors on such interactions are crucial for the development of preventive strategies to reduce morbidity and mortality and to improve the quality of life among the elderly. Based on gained knowledge, reliable and efficient warning systems can be built for enteric infections, including emerging pathogens; the most vulnerable geographic areas can be identified; and surveillance systems can be substantially improved nation-wide.